In order to be able to travel to the past, three conditions should be fulfilled:
1. Einstein's General Relativity is a valid description of the universe.
2. The Universe has a suitable structure probably incorporating sufficiently fast rotation.
3. The practical difficulties can be overcome.
My personal views on these three points are:
1. Yes. A basically simple (oh well) and beautiful theory giving several verified predictions and so far fully consistent with experiments
2. Most probably no (as indicated by the isotropy of background radiation)
3. No way. Keeping you and the rocket going for, say, ten billion years is not exactly an easy task.
There is however an easier way to violate causality if requirements 1 and 2 are met: Sending messages by radio. If the universe is inhabited by civilizations, you could send a message to one of them with instructions on how to forward the message to the next civilization, and so forth back to Earth. You don't have to wait for long to see whether the chain of transmissions has been successful; in fact, you should already have received the message...
Jeebus, the rotation part is no longer strictly necessary, as Professor kaku explains in the interview. Worm holes can do it and so can warp drive "metric engineering" like the Alcubierre drive. All it takes is supertechnology and negative energy.
I think math theorists really need to explain some things of the "past" and present (for example the fractal geometry and astronomical signs in wheat fields and filmed lights traveling above them) before looking "beyond" the outer space.
Dr.Vladimir Poponin set DNA in a tube, irradiated it with laser. Captured the light and formed an helix spiral like a crystal. When DNA was removed, the LIGHT CONTINUED SPINNING BY ITSELF, looking like violet light coming out from the pyramidion with the help of Tesla Coil. Austrian scientist, Anton Zeilenger, bended photons like multiple DNA in angular orbital moment. In Switzerland, CERN Large Hadron Collider experiences want to generate mini black holes with little entropy at a rate of 1 per second. It seems these are bubbles of vacuum. In Los Alamos National Laboratory and South Carolina Univ., they are examining the “gravastars” and they try to create super-atoms. Gravity has not been detected in space lesser than 1 mm.
These DOUBLE SNAKE energy was known in the past, though that's a long issue: www.sitchin.com/adam.htm www.keelynet.com/unclass/hardy1.htm